1. Technical Field
This invention relates generally to desktop chargers for rechargeable battery packs, and more specifically to a charger having a pocket with oblique coupling rails to retain a battery pack within the pocket for charging.
2. Background Art
Portable electronic devices, like two-way radios and mobile phones for example, owe their portability to rechargeable battery packs. Rechargeable battery packs conveniently supply power to these portable devices without the need for wires, plugs or electrical outlets. In other words, when using a mobile device with a rechargeable battery pack, the user may take the device anywhere—at any time—without the need of being continually tethered to a wall outlet.
Rechargeable battery packs typically include one or more rechargeable electrochemical cells that store and deliver electrical energy. These electrochemical cells, which may be coupled to circuitry within the pack for charging or safety, must be recharged when depleted to remain functional. While charging may be accomplished by simply plugging a wired connector from a power supply into the battery pack, many people prefer the convenience of desktop chargers to facilitate the recharging process. When using a desktop charger, the user simply inserts either a spare rechargeable battery pack or electronic device itself into the charger. The charger then detects the presence of the battery or device and begins to recharge the cells in accordance with a predetermined charging procedure. Batteries and devices for industrial use, like the two-way radios used by fire and police departments, typically stand vertically within the charger when charging. The radio, standing in this vertical position, remains easily accessible and visible to the user.
To keep these large batteries from tipping over when charging, some manufacturers have incorporated battery retention systems into the chargers and their corresponding rechargeable battery packs. One example of a prior art battery retention system can be seen in FIGS. 1 and 2. FIG. 1 illustrates a perspective view of a battery pack 100 with such a prior art battery retention system, while FIG. 2 illustrates a cross-sectional view of the battery pack 100.
In this prior art battery retention system, the battery pack 100 is equipped with two channels 102, or slots, which run lengthwise along the battery pack housing on opposite sides of the battery pack 100. These channels 102 are perpendicular to the opposing sides upon which they are disposed.
A battery charger for this battery 100, which includes a pocket into which the battery 100 may be inserted for charging, would include two rails disposed on opposite sides of the pocket. The two rails are disposed in such a manner that when the battery pack 100 is inserted into the pocket, the two rails are aligned with the channels 102 of the battery pack 100. The alignment of the rails with the channels 102 ensures that electrical contacts disposed within the pocket of the charger couple securely and consistently with charging contacts 101 disposed on the battery pack 100.
The problem with this prior art battery retention system is that some batteries, often made for the same radio, are thicker than others. Consequently, for the fixed ribs and slots of this prior art retention system the pocket of the charger must be bigger than the smallest battery. Were this not the case, the largest battery could not be charged in the charger. This problem can be seen in FIG. 3.
In FIG. 3 a charger pocket 300 having rails 301 and a back member 302 is shown. To accommodate multiple size batteries, the back member 302 must be sufficiently far from the rails 301 so as to accommodate the maximum thickness of the battery extending from the slots 102. As can be seen from FIG. 3, when a smaller battery 100 is inserted into the pocket 300, the slots 102 and rails 301 align as previously described. Since the back 103 of the battery 100 does not extend all the way to the back 302 of the charger pocket 300 when the slots 102 and rails 301 align, there will be a gap 303 between the back 103 of the battery 100 and the back 302 of the charger pocket 300. If the electrical contacts in the pocket extend through openings in the back 302 of the pocket 300, the gap 303 may become sufficiently large that the electrical contacts do not connect with the charger contacts of the battery pack 100. In such a scenario, reliable recharging of the battery pack 100 could be compromised.
A second problem arises when battery packs become smaller and smaller. To get the same amount of energy from a smaller battery pack, designers will reduce the thickness of the plastic exterior housing. In so doing, the thickness of the plastic exterior housing may be reduced to such an extent that slots can no longer accommodated. Since the charger-to-battery connection relies upon the rail-to-slot connection, designers must add extra plastic about the base edges of the battery pack just to accommodate the slots. These bumps of extra plastic material, often referred to as “rocket boosters”, can make the overall appearance of the battery pack unsightly.
There is thus a need for an improved battery housing having a contact retention system that accommodates battery packs of varying thicknesses and does not require the use of extra material on the exterior of the battery pack housing.